That already exists in the demons of chaos and the Night Gaunt, Mindflayer, Shoggoth, Wendigo, and Atlach Nacha breeds.
"According to legend, in the age of the former demon lord, wicked demons of chaos who possessed a power that was even greater than that of the gods existed there at the bottom of the sea. At the time, Poseidon was still one of the divinities ruled by the chief god, and the rule of the sea was split between her and them. It is said that the demons of chaos were sealed in the deep layer after a war, and even now, the demons of chaos are biding their time to make a comeback and once again reclaim dominion over the sea.
Those who sunk into the depths of the sea, male and female, are also kin to all monsters, so they've probably assumed the female form, and had their thought patterns changed accordingly, but no one has ever been able to confirm it, and the truth of this is uncertain."
In MGE they have the special ability to grant their husbands the ability to transform back and forth into monstrous lovecraftian forms to fuck them with.